Two-dimensional materials have served as a rich playground to study emerging phenomena and exotic physics at low dimensions. Since the discovery of graphene, atomically thin materials of many different electronic and magnetic properties have been identified experimentally. The most recent additions are 2D topological insulators and 2D magnets. In this talk, I will present our recent studies on two of these materials, WTe2 and CrI3, with scanning probe microscopy. In the first part, we use microwave impedance microscopy to directly image the edge conduction in monolayer WTe2. The observed behaviors are fully consistent with the expectations for topological edge states, and also reveal many details about the edge conduction that are important for improving transport studies. In the second part, we apply magnetic force microscopy to study thin CrI3 flakes. By probing the magnetic switching process in CrI3, we find that two types of magnetic orders coexist in these flakes, one at surface and the other inside the bulk, corresponding to different layer stacking orders.

简介：Yongtao Cui is an Assistant Professor in the Department of Physics and Astronomy at the University of California, Riverside. He obtained his BS in Physics from Peking University in 2005, and his PhD degree in Applied Physics from Cornell University in 2011. He then moved to Stanford University for postdoc research on the development of Microwave Impedance Microscopy and its applications on the study of quantum materials. He joined UC Riverside in the summer of 2016.